code: def imread_opencv(filename):
      """OpenCV image loader with identity 2D affine."""
      cv2 = require_module("cv2")
      img = cv2.imread(filename, flags=-1)
      if img is None:
          raise IOError(filename)
      return image2nibabel(img[..., ::-1])
  
file_path: NiftyNet/niftynet/io/image_loader.py
imports: from collections import OrderedDict
  import nibabel
  import numpy
  import tensorflow
  from niftynet.utilities.util_import import require_module
label_desc: Use image node_id 4 for calling a global function with example usage: imread_opencv(filename) and returns: image2nibabel